Howard Kuljian and his family were out for a walk on a damp, overcast morning at Big Lagoon state beach, playing fetch with their dog Fran as 2.5 to 3 metre surf churned the nearby water like a washing machine.

Kuljian tossed a stick that took the dog down to the water's edge, and in an instant, authorities said, a wave swallowed it, setting off a nightmarish scramble.

In the end, Kuljian, 54, his wife Mary Scott, 57, and son Gregory "Geddie" Kuljian were all engulfed by the roiling waters after trying to save the dog, then each other. The two parents' bodies were later recovered, but the Coast Guard called off a search for the boy.

The Humboldt County coroner's office said today (NZ time) that the body of the 16-year-old boy still had not been found.

The couple's 18-year-old daughter, Olivia, and Gregory's girlfriend could only watch from the beach as the horror unfolded. The dog later made its way safely back onto the beach.

Mourners wore green again today in a gut-wrenching tribute to teenage boy. Students at Arcata High School wore his favourite colour as they tried to come to terms with the sudden, tragic loss of the well-liked family.

"His parents treated me like I was one of their own. They treated everyone like their own children no matter who it was," said Jacob Swindle, a close friend of the family.

More than 1600 people "liked" a Facebook page set up by the teenager's friends called "Wear Green for Geddie" - using his nickname. Dozens tweeted tributes with #WearGreenForGeddie.

"I will always remember him no matter how long," wrote Emmalaya Owen on the Facebook page. "Especially how he was such an upbeat happy person or how he tried to put up `Be Happy' propaganda posters he drew around school."

At Big Lagoon beach, a short drive from Arcata, signs posted near the parking lot warned beachgoers not to turn their back to the surf and to pay special attention to sneaker waves.

A steep slope of beach leads to the water's edge, where waves break with a boom right on shore. Officials warn beachgoers not to turn their backs to the water.

On Saturday, as the family walked along the beach, Howard Kuljian threw the stick and the dog gave chase, said Dana Jones, a state parks district superintendent.

Seeing his son in the water, Kuljian leapt to action, and disappeared into the frigid water.

Gregory managed to pull himself back onto the sand, but after realising his father was drowning, both he and his mother went in to save him.

A nearby bystander called police. By the time help arrived, it was too late.

Jones said the officer wasn't able to get to the family members because of the high surf.